Submission #1046171

#	Time	Username	Problem	Language	Result	Execution time	Memory
1046171		vladilius	Mergers (JOI19_mergers)	C++17	100 / 100	503 ms	132256 KiB

mergers

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define pb push_back
#define ff first
#define ss second
#define ins insert

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int n, k; cin>>n>>k;
    vector<int> g[n + 1];
    for (int i = 1; i < n; i++){
        int x, y; cin>>x>>y;
        g[x].pb(y);
        g[y].pb(x);
    }
    vector<int> s(n + 1), all[k + 1];
    for (int i = 1; i <= n; i++){
        cin>>s[i];
        all[s[i]].pb(i);
    }
    
    vector<int> sz(n + 1), h(n + 1), d(n + 1), p(n + 1);
    function<void(int, int)> fill = [&](int v, int pr){
        p[v] = pr;
        d[v] = d[pr] + 1;
        sz[v] = 1;
        for (int i: g[v]){
            if (i == pr) continue;
            fill(i, v);
            if (sz[i] > sz[h[v]]){
                h[v] = i;
            }
            sz[v] += sz[i];
        }
    };
    fill(1, 0);
    
    vector<int> head(n + 1), pos(n + 1);
    int timer = 0;
    function<void(int, int)> fill_hld = [&](int v, int k){
        head[v] = k;
        pos[v] = ++timer;
        if (!h[v]) return;
        fill_hld(h[v], k);
        for (int i: g[v]){
            if (pos[i]) continue;
            fill_hld(i, i);
        }
    };
    fill_hld(1, 1);
    
    set<int> st;
    for (int i = 2; i <= n; i++) st.ins(i);
    
    vector<int> a(n + 2);
    
    auto rem = [&](int l, int r){
        a[l]++; a[r + 1]--;
    };
    
    auto upd = [&](int x, int y){
        while (head[x] != head[y]){
            if (d[head[x]] > d[head[y]]){
                swap(x, y);
            }
            rem(pos[head[y]], pos[y]);
            y = p[head[y]];
        }
        if (d[x] > d[y]) swap(x, y);
        rem(pos[x] + 1, pos[y]);
    };
    
    for (int i = 1; i <= k; i++){
        for (int j = 0; j + 1 < all[i].size(); j++){
            upd(all[i][j], all[i][j + 1]);
        }
    }
    
    vector<int> inv(n + 1), pr(n + 1);
    for (int i = 1; i <= n; i++){
        inv[pos[i]] = i;
        pr[i] = pr[i - 1] + a[i];
    }
    
    vector<bool> ban(n + 1);
    vector<int> bd;
    for (int i = 2; i <= n; i++){
        if (!pr[i]){
            bd.pb(inv[i]);
            ban[inv[i]] = 1;
        }
    }
    
    auto f = [&](int x, int y){
        return (d[x] > d[y]) ? x : y;
    };
    
    vector<int> gr(n + 1);
    timer = 0;
    function<void(int)> dfs = [&](int v){
        gr[v] = timer;
        for (int i: g[v]){
            if (gr[i] || ban[f(i, v)]) continue;
            dfs(i);
        }
    };
    
    for (int i = 1; i <= n; i++){
        if (!gr[i]){
            timer++;
            dfs(i);
        }
    }
    
    if (timer == 1){
        cout<<0<<"\n";
        return 0;
    }
    
    vector<int> cc(timer + 1);
    
    for (int i: bd){
        cc[gr[i]]++;
        cc[gr[p[i]]]++;
    }
    
    int tot = 0;
    for (int i = 1; i <= timer; i++) tot += (cc[i] == 1);
    
    cout<<(tot + 1) / 2<<"\n";
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:80:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   80 |         for (int j = 0; j + 1 < all[i].size(); j++){
      |                         ~~~~~~^~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 24 / 24
• Subtask 3: 14 / 14
• Subtask 4: 22 / 22
• Subtask 5: 30 / 30